Infective endocarditis is still an important disease that accounts for 0.3-3.0/1000 of all hospital admissions and the viridans streptococci remain the most frequent cause of subacute bacterial endocarditis. In this group of streptococci, S. mitis and the nutritionally variant streptococci, account for 35-40% of the disease in man. To date, there has not been a comprehensive analysis of the surface components of these strains. The overall objective of this research proposal, therefore is a systematic study of the surface components of these two types of streptococci in order to better understand the interaction of these bacteria with the heart valve during the disease process. Toward this objective we plan to chemically and structurally analyze the surface components (peptidoglycan, carbohydrates, protein, and amphipathic molecules). In addition, we will initiate immunochemical characterizations of the important surface components to compare strains within each group as well as between the groups. Finally, these studies will include comparisons of the surface components from bacteria grown in semi-synthetic medium as compared to supplemental complex medium and the surface components of exponential and stationary phase organisms. The chemical and immunological studies will conclude with functional studies into the structure-function relationship of the attachment process of the bacteria to the cardiac valve during the disease process. Both a rabbit endocarditis model and fibrinplatelet adherence assay will be used to analyze the attachment process and the surface components involved in it. The knowledge gained from the proposed studies will permit the laboratory technician to isolate and rapidly identify the nutritionally variant streptococci from blood cultures, permit the antibiotic regimen to commence and continue for the proper period of time, and perhaps provide information for a potential vaccine against these groups of organisms for the population at risk. Infective endocarditis is a serious disease in that if not treated rapidly and properly, secondary complications arise including renal and neurological damage. However, 60% of the deaths caused by this disease is due to congestive heart failure.